When my clients first come to me asking how to finally lose fat without feeling miserable, one question comes up again and again: “Can I combine intermittent fasting and IIFYM to get better results?”
I’m Anthony Collova, founder of IIFYM and creator of the original Macro Calculator. I’ve spent years helping thousands of people break free from restrictive diets and find a sustainable way to eat. And here’s what I tell them: Yes, intermittent fasting and IIFYM work incredibly well together, if you do it right.
In this article, I’m going to walk you through exactly how these two methods can support your fat loss goals, why they pair so well, and how you can apply this combo in your own life. I’ll also share what the latest research says, along with some of the common mistakes to avoid.
Let’s get into it.
What Is Intermittent Fasting?
Intermittent fasting is a simple way to structure your eating schedule. It sets clear windows for when to eat and when to fast. One of the most popular methods is the 16:8 approach. So, you fast for 16 hours and eat during an 8-hour window. Most people skip breakfast and start eating around noon, finishing their last meal by 8 PM.
Other approaches include 5:2 fasting, where you eat normally for five days and restrict calories for two, and alternate-day fasting, which involves fasting every other day. The 16:8 method tends to be the easiest to follow and fit into daily routines.
Time-restricted feeding helps reduce snacking, mindless eating, and late-night meals. It limits the number of times you eat, which often lowers your total calorie intake without counting every bite.
Intermittent fasting also affects how your body uses energy. When you stop eating for an extended period, your body shifts from using glucose to using fat for fuel. This process is called the metabolic switch. It helps your body tap into stored fat, which supports weight loss.
One of the most discussed benefits of intermittent fasting is autophagy. This is the body’s natural process of cleaning out damaged cells. It may support cellular health, although more research is still underway.
Beyond fat loss, studies show that intermittent fasting may support insulin sensitivity, mental clarity, and appetite control. It may also improve hormone function linked to metabolism and hunger regulation.
Many people find it easier to stick to a routine that doesn’t require constant eating or planning six meals a day. It simplifies your eating pattern without cutting out entire food groups.
If you’re already tracking your food with a macro-based plan, fasting can make it easier to manage portions and hit your targets. You’ll be working with fewer meals, which often leads to more mindful choices.
What Is IIFYM ?
IIFYM stands for “If It Fits Your Macros.” It’s a way of eating that focuses on hitting daily targets for protein, carbs, and fats i.e. your macronutrients. Instead of avoiding specific foods, you eat what you enjoy as long as it fits within your daily macro goals.
Macro tracking for weight loss helps you stay in control without the restrictions of traditional dieting. You get structure and flexibility at the same time. You don’t need to cut out entire food groups or stick to bland meals. If a food fits your macros, it works.
To follow IIFYM, you first calculate your macro needs. This depends on your age, weight, activity level, and fat loss goals. A macro calculator can help you find the right daily numbers for protein, carbohydrates, and fats.
Protein is important when cutting fat. It helps you preserve muscle and stay full between meals. Carbs and fats support energy, recovery, and hormone health. The right carb-fat balance depends on your personal preference and how your body responds.
Flexible dieting means you’re not locked into a rigid meal plan. You can eat different foods each day and still stay on track. Whether it’s chicken and rice or a sandwich with chips, it’s the overall balance that counts.
IIFYM shifts the focus from just cutting calories to making sure your body gets what it needs. You’ll start to understand what’s in your food and how it impacts your progress. It gives you more freedom while still driving results.
This method works for busy schedules, social events, and travel. You don’t need to carry pre-packed meals everywhere. You learn how to make better choices, not perfect ones.
IIFYM is also about building awareness. When you know your numbers, you can adjust based on your goals. Whether you’re cutting fat, maintaining, or building muscle, your macros guide the way.
Using a macro tracker app makes it easier to log meals and stay consistent. Over time, you get faster and more accurate with your food choices.
Scientific Research Supporting Intermittent Fasting And IIFYM Combo
There is a growing body of research examining the combined effects of intermittent fasting and macro tracking. Studies suggest that using both methods together may support fat loss, lean muscle retention, and improved dietary adherence.
One study by Isenmann et al. (2021) compared time-restricted feeding with macro-based dieting across several weeks. Participants in both groups reduced calorie intake and monitored protein consumption. The group that followed both time-restricted eating and macro tracking showed notable outcomes in body composition.
Key findings from the study included:
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Greater fat loss, especially around the waist
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No significant loss of muscle mass, even in a calorie deficit
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Higher adherence rates over the course of the study
Research indicates that time-restricted eating simplifies meal timing, while macro tracking provides structure to nutritional intake. When both are applied, the result appears to be a combination of flexibility and consistency.
A separate study published in Cell Metabolism explored the effects of early time-restricted feeding. It found that limiting the eating window improved insulin sensitivity, reduced blood pressure, and lowered oxidative stress markers. These results were observed even without weight loss, suggesting potential metabolic benefits of intermittent fasting on its own.
Macro tracking contributes by ensuring adequate protein intake, which is important during fat loss phases for preserving lean muscle mass. Tracking carbs and fats based on individual activity levels may also help support energy levels and recovery.
In addition, a 2020 review of flexible dieting reported that individuals following IIFYM principles were more likely to maintain weight loss over time. The review highlighted that flexible approaches to eating were linked to better long-term dietary adherence compared to rigid meal plans.
| Training Stage | Muscle Gain Potential (Men) | Muscle Gain Potential (Women) |
| Novice | 1–1.5% of body weight (~1.5–2.5 lbs) | 0.5–0.75% of body weight (~0.65–1 lb) |
| Intermediate | 0.5–0.75% of body weight (~0.75–1.25 lbs) | 0.25–0.375% of body weight (~0.325–0.5 lbs) |
| Experienced | 0.25–0.375% of body weight (~0.375–0.625 lbs) | 0.125–0.1875% of body weight (~0.1625–0.25 lbs) |
In summary:
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Intermittent fasting may improve metabolic flexibility
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Macro tracking helps maintain muscle and nutrient balance
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Combining both methods may lead to sustainable and effective outcomes
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The approach is adaptable and allows for structured flexibility
Some Research-Backed Benefits of Intermittent Fasting And IIFYM
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↓ Body fat
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↑ Muscle retention
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↑ Diet adherence
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↑ Insulin sensitivity
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↓ Inflammation markers
Intermittent Fasting And IIFYM: Challenges and How to Overcome Them
Combining intermittent fasting with IIFYM delivers results, but it’s not without challenges. Knowing how to handle these common hurdles helps you stay consistent and avoid setbacks.
1. Hunger During Fasting Windows
Hunger hits hardest in the first week. Stay hydrated with water, black coffee, or herbal tea. Eat more fiber-rich foods during your eating window to stay full longer. Usually, hunger fades once your body adjusts.
2, Miscalculating Macros
IIFYM only works if your macros are accurate. Many underestimate portions or forget small bites. Use a reliable macro tracker app. Weigh your food when you can. Don’t guess.
3. Undereating Protein
Protein is key for muscle maintenance and satiety. Eating fewer meals makes it easy to fall short. Prioritize protein at every meal. Lean meats, eggs, Greek yogurt, and plant-based proteins are solid choices.
4. Fat Loss Plateaus
Your progress will slow as your body adapts. If fat loss stalls, revisit your macro targets and activity level. Small calorie tweaks or adding movement can reignite progress. Avoid drastic changes consistency wins.
5. Adherence Struggles
Some struggle to balance fasting and macros. Start simple: try a 16:8 fasting schedule. Focus on hitting your protein and calorie goals first. Add more complexity only when you’re comfortable with the basics.
🎯 Quick Tip:
If you hit plateaus or struggle with consistency, check out our macro tracking guide or download the macro cheat sheet. Simplify your routine and keep moving forward.
How to Start: Your Step-by-Step Guide to Combining Intermittent Fasting And IIFYM
Getting started is easier than you think. Follow these steps to build your plan and reach your fat loss goals.
1.Pick Your Fasting Protocol
Start with a popular schedule like 16:8 fast for 16 hours, eat in an 8-hour window. It fits most lifestyles and naturally reduces calories without overwhelm.
2. Calculate Your Macros
Use an IIFYM macro calculator to find your daily protein, carb, and fat targets based on your goals, weight, and activity. This gives you clear numbers to hit during your eating window.
3. Plan Your Meals
Within your eating window, organize meals that hit your macro targets. Focus on whole foods rich in protein and fiber to stay full and energized. Planning prevents impulsive eating.
4. Track Your Intake
Log your meals and snacks with a macro tracker app. Tracking builds awareness and keeps you accountable. Many apps include barcode scanners to make it easy.
5. Adjust and Improve
Check your progress weekly. If fat loss stalls, tweak your macros or adjust your fasting window. Stay flexible and patient your body needs time to adapt.
Should You Combine Intermittent Fasting And IIFYM?
After working with thousands of clients and creating the original Macro Calculator, I’ve seen firsthand what actually works in the real world. And I’ll say this clearly: IIFYM doesn’t need to be paired with any other strategy to be effective.
It stands on its own because it’s simple, flexible, and sustainable. You don’t need to follow strict rules, cut out entire food groups, or time your meals down to the minute. With IIFYM, you get structure through your macros, and freedom in how you reach them. That’s what makes it powerful.
People often search for the “perfect” diet by stacking multiple systems together. But the truth is, complicating your nutrition doesn’t lead to better results, it usually leads to burnout.
IIFYM works because it’s built around the fundamentals: eat the right amount of protein, carbs, and fats for your goals. Track consistently. Make informed food choices. That’s it.
If you’re focused on fat loss, muscle gain, or just maintaining a healthy lifestyle, IIFYM gives you the tools to get there without giving up your favorite foods or your freedom.
It’s not a trend. It’s a system based on logic, backed by science, and proven by experience.
And that’s why it works.
Get Started with IIFYM Tools and Coaching
Start your fat loss journey with the right tools and support. Use the IIFYM Macro Calculator to find your perfect macro targets based on your goals and lifestyle.
Track your daily intake with our easy-to-use Macro Tracker App. It helps you stay on target and adjust as needed to keep progress steady.
For personalized guidance, explore our Custom Macro Plans. These plans fit your needs and make flexible dieting simple.
Join our Weight Loss Programs for expert advice, motivation, and accountability. Coaching helps you overcome challenges and stay consistent.
Take control today. Click below to:
- Calculate Your Macros Now: Find your perfect targets based on your goals and lifestyle with our IIFYM Macro Calculator.
- Track Your Progress with the IIFYM App: Easily log your meals, stay on target, and adjust as needed for steady progress.
- Join Our Fat Loss Coaching Program: Get expert guidance, motivation, and accountability to overcome challenges and stay consistent.
Take control today with tools and coaching that make fat loss simple, effective, and sustainable.
References
Isenmann, E., Dissemond, J., & Geisler, S. (2021). The effects of a macronutrient-based diet and time-restricted feeding (16:8) on body composition in physically active individuals: A 14-week randomised controlled trial. Nutrients, 13(9), 3122.
Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8465090/
Johns Hopkins Medicine. Intermittent Fasting: What is it, and how does it work?
Available from: https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work
Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. Nutrients, 11(10), 2442.
Available from: https://www.mdpi.com/2072-6643/11/10/2442
Brogi, S., Tabanelli, R., Puca, S., & Calderone, V. (2024). Intermittent fasting: Myths, fakes and truth on this dietary regimen approach. Nutrients.
Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC11241639/
